Gray Whales: Weathering Change?
With Comments from Wayne Perryman, Biologist
Wayne Perryman is the government's leading expert on gray whale cows and calves. He counts them each spring as they pass the California coast at Pt. Piedras Blancas on their way to Alaska.


A Changing Environment
Mr. Perryman reminds us, “Most of the eastern Pacific population of gray whales feeds in the Arctic during the summer to early fall. That environment has changed significantly over the past 15 years. As the climate warms, ice gets thinner and it covers less area. This change impacts a wide range of marine mammals (seals, walrus, whales, polar bears). Right now, we can feel comfortable saying that gray whales are feeding in different places (farther north) and on different prey than they did back in the 1980s."

Changes in Feeding Areas
Before leaving their arctic homes and migrating south to Baja Mexico, gray whales feast on tiny crustaceans that live on the ocean floor. This is how whales put on thick layers of blubber to help sustain them during their migration south, the winter in Mexico's lagoons, and the return migration north. As warmer waters melt the sea ice, other animals move into the whales' feeding grounds. Crowded by the new competition for food, gray whales then must travel further north and feed longer to get filled up and gain blubber.

Changes in Migration Timing
Changes in the Arctic, say scientists, have disrupted the timing of the whales' yearly migration.
Whale watchers and marine scientists note that gray whales have been delaying their southward migrations as they stay longer to eat. For example, compared to two decades ago, gray whales are reaching the Monterey Bay area a week or more later. "This isn't trivial," says Mr. Perryman. "It's a significant change."

"It takes a long-time series of data to know how this is affecting the whale population. Climate changes slowly in the long term while weather can fluctuate widely in the sort term, so it takes time to tease out the long-term effects from the short-term ones.

Changes in Population Growth
"It appears that growth of the gray whale population has slowed and may have stopped. Also, reproduction (indicated by number of calves migrating north) has fluctuated widely, and in general has been lower than we would expect for a growing population. How this all fits into the puzzle of climate change effects is a good question. Perhaps YOU will become a scientist and help to figure it out!"

Try This! Journal Questions
  • Read more about Mr. Perryman here. Think about how his life prepared him for the job he has today. What things do YOU enjoy doing that might lead to enjoyable work in your future?
  • What would be some consequences for the gray whale food supply if arctic ice continues to melt later and to cover less area?
  • How might changes in the whales' migration schedule affect these mammals in the future?
  • Of the challenges you know about today, which do you think are most important for scientists to be studying? Explain.
  • Find out more about gray whales and list factors that might make the species' population decrease.